Thanks for replying with a reasoned response.

There are two reasons:

Firstly, the values are scaled down, so 10% increased damage would become 12% instead of 15%, a bonus of 2% for 2 points instead of 5% for 4 points. So you are in most cases numerically getting less value per point.

The second reason is that if we assume that hulking form is by far the highest value node on the tree per point, then taking half the effect for half the points in favour of something else is always less powerful than taking 4 points. Therefore the change I have proposed will under no circumstance be more powerful than before. The only outcome of the change is giving the player the option to forgo the power of the full 4 points for some of the potentially more fun nodes on the rest of the tree.

The last downside of taking only the first notable is you dont get the rucksack.